1. Field of the Invention
The present invention relates generally to the coating of relatively large generally horizontal surfaces such as roads, driveways, parking lots, tennis courts, flat roofs, rain water catchments and similar surfaces of which embrace sufficient areas to warrant the use of a machine to effect coating application. For convenience these surfaces are herein referred to as "traffic surfaces", it being understood that this term is not used in any restrictive sense and is not confined, for example, to surfaces which accommodate vehicular traffic.
2. Prior Art
Traffic surfaces are exposed to wear and often to the effects of the elements with the result that they ae subject to deterioration. They accordingly require protective coatings to extend their useful lives. These coatings may be applied at the time the surface is constructed, but are more frequently required after a certain amount of use in order to restore the surface to a desirable condition and to overcome the effect that spalling, minor cracks and the like may have had in accelerating surface deterioration.
In some cases these coatings can be applied manually with long handled applicators; however, if the area to be treated is sufficiently large, it is preferably treated by mobile equipment such as machines which have a tank for the liquid or slurry type of coating material, dispensing apparatus for metering the coating material onto the surface to be treated, and mechanism for spreading the applied coating in a thin layer upon the surface. In some cases, it is advisable to apply particulate material such as sand to the surface to improve its frictional properties, and this has been done by separately applying the sand through its own dispensing mechanism upon the already coated surface where it partakes somewhat of the spreading action of the devices such as elongate squeegees and/or paddle wheel assemblies which are used to smooth and level the liquid coating material.
Machines of the type described in the preceding paragraph have significant limitations. For one thing they are essentially single purpose machines in that they can apply to the surface being treated only the one material with which the tank has been charged, except that sand can be either added or withheld at the operator's option. Such machines are not equipped to substantially vary the composition of the coating during application, nor are they capable of applying coating materials, such as epoxy coatings, whose ingredients, once combined, set up by chemical action and have a rather short period after being mixed during which they can be successfully stored and dispensed. These machines are likewise incapable of handling coating materials which involve problems such as a tendency of the liquids and or solids to separate rapidly so that uniform consistency of a batch in the supply tank is short-lived.
Another respect in which the prior art machines are limited is that they are essentially large area machines intended mainly for travelling along highways in a basically unidirectional fashion, and are incapable of working in constricted or unusually shaped areas. Moreover the spreading and leveling devices with which these machines are equipped are capable of treating only surfaces which have a high degree of flatness lateral to the primary direction of machine travel. Moreover, such machines cannot execute immediate reversals in direction to correct or supplement the coating being applied.